May be the question has been discussed in another section of the board under different aspects but beacuse the rule of 80% reusability it might be worth to discuss techniques and methods of deflatability here.

The Space Shuttle releases the big external expendable tank after reaching the orbit and the tank is lost.This has been critized several times at this board as well as in the general public. I myself several times have discussed the possibility to rescue the expendable tank or the expendable stages of the Falcon or other rockets.

Is it theoretically possible to construct and build a deflatable tank? Which theoretical ways could be found?

Something that is empty in principle could be deflated and kept onboard of a vehicle. It could be reused later after it has been filled again.

Wouldnt it be an option to 'simply' give every stage of the rocket its own wings so it can glide back to earth and then reuse it again? It wouldnt be that much of greater weight in total i believe, though much more expensive since you need small computers for control unless you pilot it with a remote control.

I have thinking about tis option earlier already - if there are stages at least one of them would reach a velocity close to orbital velocity I suppose but I may be wrong. If I'm right then this stage would need a heat protection shield as the orbiting vehicle needs for reentry. And there is the question wether the wings will be able to resist the forces.

Additionaly the winged stage as well as the first stage require additional infrastructure to find and rescue them.

In other threads there have been significant doubts about rescuing stages that reach velocities close to orbtal velocities.

The question of deflatable tanks as well as the question of rescuing stages in the first line have the purpose to leave all the well-known paths that seem to indicate remarkable obstacles for Scaled/Mojave etc. to get to the orbit. So these firms and teams really may continue to try new ways most people don't imagine.